5.1.1.4 Mutual Authentication
[MS-DRSR] sections 2.2.2 and 2.2.4 specify the mutual authentication requirements for client-to-DC interactions over the RPC interfaces documented in [MS-DRSR]. The requirements are the same for mutual authentication in an LDAP connection.
Therefore, by registering its SPNs (2) for the RPC interfaces documented in [MS-DRSR], a DC also satisfies its SPN (2) registration requirements for LDAP.